1. Field of the Invention
The invention concerns torsional damper devices of the type used in the construction of a motor vehicle friction clutch, for example.
2. Description of Related Art
Torsional damper devices of the above kind usually include, between an input member and an output member rotatable relative to each other, two dampers which, in kinematic terms, come into action successively upon relative angular movement between the input member and the output member, namely, in the reverse order to that in which they come into action, a main damper and a pre-damper, each of these dampers including two guide washers which, disposed on respective opposite axial sides of a web, are rotatable relative to the web, circumferentially acting spring means disposed circumferentially between the guide washers and the web, and friction means which, operative between the guide washers and the web or parts constrained to rotate therewith, are acted on by axially acting spring means.
In the construction of a friction clutch the input member is for example a disc which carries friction linings at its periphery which are clamped between the pressure plate and the reaction plate of the clutch and the output member is for example a hub adapted to be constrained to rotate with the input shaft of a gearbox.
The function of the dampers is to filter out vibrations caused by the engine, when idling in the case of the pre-damper and in normal operation in the case of the main damper.
To satisfy particular operating conditions document FR-A-2 735 548, to which this patent application explicitly refers, proposes the provision of a third or intermediate damper which comes into action after the pre-damper and before the main damper.
The above document also proposes pre-assembly of some of the components to form sub-assemblies, in order to reduce assembly time.
Accordingly, a first sub-assembly, in which the pre-damper is pre-assembled to the output member and/or a second sub-assembly in which a friction washer forming part of the friction means of the main damper is pre-assembled to the guide washer of the main damper at the shorter distance from the friction washer can be provided, if required.